The third-year player will be sidelined two to four weeks after breaking his right middle finger in practice Sunday. He broke his right forearm during his rookie season in 2006.
Adeyanju, a fourth-round pick who started seven games last year, was sent back to St. Louis on Monday to have pins inserted. Coach Scott Linehan said it could be as short as two weeks and as long as a month before Adeyanju is cleared to return.
He's competing for a backup spot at end after the Rams took Chris Long with the second pick of the draft. Adeyanju started nine games his rookie season after the Rams traded Anthony Hargrove to Buffalo in a disciplinary move, and is perhaps the team's best run defender.
"Once he gets that wound healed he'll be able to get some work done with a club on that hand," Linehan said. "It's a complete fluke deal."
Safety Oshiomogho Atogwe and tight end Anthony Becht were both held out of the afternoon workout due to hamstring issues, and the team was unclear when either would return. Linebacker Chris Draft missed most of the day due to lower back tightness.
"These are the dog days of training camp, and this is the part we've got to get through and still get our work done," Linehan said.
The Rams added depth in a secondary missing Fakhir Brown (shoulder) for perhaps two weeks, signing cornerback Cortney Grixby, and also claimed offensive tackle Julius Wilson off waivers from the Dolphins.
Grixby, who played at Nebraska, was released by the Panthers on July 15 after signing as an undrafted player. Rookie offensive tackle Stephen Sene was released and rookie defensive tackle Josh Thompson is likely to be released with an injury settlement after rupturing the plantar fascia on his left foot.